In the field of photography, the lens is a vital tool of the camera that function to focus light to medium burns catcher (or more commonly known by the name of the movie). Consists of several distinct lenses that can be arranged so that the result size of the image capture and focus the different variations.

On the outside of the lens photography usually placed three ring regulator, namely the focal length of the ring (for the lens type of variable), the ring diaphragm, and the focus ring.

A. Focus
Is part of the lens sharpness set the distance

B. Diafragma
Is part of the opening set the shutter

Lens Type:

A. Macro lens

Macro lens is the lens focal length is designed for very short. This lens is specifically used      to capture the maximum detail of an object. Many are used for product pictures and science and      biology.

B. Single focus lens

Single focus lens is a lens with a single focal plane, usually set at a distance hiperfokal.    Single focus lens designed to achieve the maximum focal distance that can reach depths of space    range from a short distance to the farthest distance (distance hiperfokal)

C. Parfokal lens

Parfokal lens is a lens that maintain the sharpness of its focus areas despite the lens focal    length changes.

D. Soft focus lens

Soft Focus is a photographic effect on the blur caused by the aberration due speris. A soft    focus lens is designed to blurring effects while still maintaining the sharpness of each line of    the subject. Soft focus effects caused by the lens is not the same as out of focus effects    caused by the subject’s position outside the focal plane. Examples of soft focus lens is the    Canon EF 135mm f / 2.8 with Softfocus and Pentax SMC 28mm f / 2.8 Lens Soft FA. Both are    equipped with the system settings speris aberration, if it is turned off speris aberration, the    lens will produce images with sharp focus as the other lenses in general.

E. Wide angle lens

Wide angle lens is a lens with a shorter focal length than normal lenses, according to the size     of the image frame in the field of film [6] on film cameras, as well as dimensional image sensor    in the focal areas of digital cameras. According to the standard photography, the normal lens is    the lens that has a focal length of the field approached the focal length of the diagonal.       Wide angle lens with focal length shorter circle will project a larger image of the focal areas.

F. Fish eye lens

Fish eye lens is a wide-angle lens with the point of view a very wide hemisperis. Fish eye lens    was first designed and developed to study the importance of meteorology for the cloud line and    was first called “whole-sky lenses”, fish eye lens photography became popular in general because    the typical image distortions.

G. Telephoto lens

Telephoto lens is a lens with the construction of a shorter length than the length of the focus    so that the resulting optical center outside of the lens body. A telephoto lens can be    identified with the composition of the so-called telephoto lens group is designed to focus the      far distance. A regular lens with a shorter length of the lens than the focus length, not    necessarily a telephoto lens. But the reality of a lens with focal length above 280mm telephoto    lens always said.

If a camera lens is at 200mm focal length and focus to infinite distance, exit pupil is located    at a distance of 200mm from the focal areas and pupils into the lens optical center. When the    lens focal length is increased, the physical length of the lens body would be longer if the lens    is not a telephoto lens. But not so with a telephoto lens, telephoto lens composition of the    group making the light passed by the front of the word, as if derived from the focal length very    long before passing into the nature of focal areas of the negative focus of this lens       arrangement. Heaviest telephoto lens ever made, made by Carl Zeiss with a 1700mm focal length f    / 4 lens with a 425mm length and weighs 256 kg. Designed for medium format Hasselblad camera FE    203.

H. Variable lens

Variable lens is a lens that can not maintain the focus areas in the event of a change of focal    length for focal field position also shifted, so that any necessary re-focusing the focal length    changes. Focal length of the lens is not a single variable, but can be changed at a certain    range from the minimum value to its maximum value. The size of the variable lens is often    determined by the ratio of lens focal length of the longest and the shortest, for example, a    lens with focal length 100mm to 400mm, is described as a 4:1 or “4x” zoom.

With the technological development of modern lens, the degradation of image quality produced by    the variable lens, compared with prime lenses, it is very minimal. This is different with about    20 years ago, when the consideration to maintain the quality of the image, many professional    photographers when it chose to work with does not rely on the variable lens. Nevertheless, still    say that until the year 2009, there were no variable lens with 3x the size above which can rival    prime lens in terms of image quality. Of course this depends also on the skill of a photographer    in a set of light, maintaining the stability of the camera from shaking during the exposure time    and digital though.

I. Fixed lens

The lens is fixed focal length lens with a single. Fixed lens is often said to have more value    to the sharpness of the image. With a smaller size, the lens still has a lighter weight and    cheaper price compared to the zoom lens at the same quality. Prime lens also has an advantage in    speed and lens with a large casement diameter (small opening value), a fixed lens becomes more    reliable for use in low light shooting photography and blur effect with a low depth of field.

In English, the term in the context of prime lens was used as the opposite of zoom. A prime lens    with a single focal length and zoom lenses with variable focal length. (source:http://id.wikipedia.org/wiki/Lensa_fotografi)